Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$24.94	3.574%	$25.8314	$25.83	$25.85	$25.80
Purchase #2	$52.84	11.735%	$59.0408	$59.04	$59.05	$59.00
Purchase #3	$172.73	7.213%	$185.189	$185.19	$185.20	$185.20
Purchase #4	$138.55	3.592%	$143.5267	$143.53	$143.55	$143.50
Purchase #5	$121.58	6.536%	$129.5265	$129.53	$129.55	$129.50
Purchase #6	$136.90	5.105%	$143.8887	$143.89	$143.90	$143.90
Purchase #7	$194.88	11.689%	$217.6595	$217.66	$217.65	$217.70
7 purchase totals =	$842.42		$904.6626	$904.67	$904.75	$904.60